With the dramatic increase in the use of fossil fuels, there is an increasing demand for use of alternative energy or clean energy. The field of electricity generation and accumulation using an electrochemical reaction has been most actively studied to meet the increasing demand.
A current representative example of an electrochemical device using such electrochemical energy may include secondary batteries, and their applications have been on the gradual rise. Recently, the demand for secondary batteries as energy sources has surged with the increase in technical development and the demand for portable devices such as laptop computers, portable telephones, cameras, etc. Among such secondary batteries, a lithium secondary battery having high energy density and working potential, a long cycle lifespan, and a low self-discharge rate has been actively researched and widely used through commercialization.
Generally, a secondary battery consists of a positive electrode, a negative electrode, and an electrolyte, and is chargeable and dischargeable because it serves to transfer energy to electrodes while moving back and forth between both of the electrodes by intercalating lithium ions such as carbon particles emitted from a positive electrode active material into a negative electrode active material during a first charge and then deintercalating the lithium ions from the negative electrode active material during the discharge.
For example, the lithium secondary battery has a structure in which a lithium electrolyte is impregnated into an electrode assembly, which includes a positive electrode including a lithium transition metal oxide as an electrode active material, a negative electrode including a carbon-based active material, and a porous separator. The positive electrode is manufactured by coating an aluminum foil with a positive electrode mixture including a lithium transition metal oxide, and the negative electrode is manufactured by coating a copper foil with a negative electrode mixture including a carbon-based active material.
To check for uniformity in physical properties of a secondary battery, a technology capable of accurately measuring a distribution of a binder in a positive electrode mixture or a negative electrode mixture is required.